The thing about "inactive emails" or "reminder emails" is that they're not engaging. The user hasn't visited for a reason (they didn't like the community, they forgot, they got pissed off, etc). Just saying something like, "Hey, did you forget about us? Cause we didn't forget about you." doesn't cut it.
Newsletters work well because they contain information. They engage the reader. They're not as easily dismissed as reminder emails.
Now, somehow combine the two and you have a winning combination. Create a newsletter or an engaging email, then send it to those that haven't visited your community in 30, 60, 120 days (w/e). "WOW" them back to your community.